1. Field of the Invention
The present invention relates to an image formation apparatus having functions for automatic adjustment or maintenance.
2. Description of the Related Art
In some cases, these types of conventional image formation apparatuses have a problem in that image density changes due to the change in a photosensitive member and a developing device over time, or due to the change in the temperature or humidity in the environment where the apparatus has been situated. As a countermeasure for the above-described problem, various proposals have been made with regard to a technique wherein parameters having an influence upon the image density of a toner image, e.g., a charging bias, a developing bias, and so forth, are adjusted at a suitable timing, thereby stabilizing the image density. For example, in a case of forming a color image using multiple image carrying members, a method of controlling toner density (Japanese Patent Laid-Open No. 63-147177), and a method of controlling an exposure amount (Japanese Patent Laid-Open No. 63-280275, are known wherein control is performed based upon detected information with regard to a predetermined pattern (test patch) transferred onto transfer means such as a common transfer belt or the like for transferring each visible image on the image carrying member onto a transfer member.
Furthermore, a method is known wherein the aforementioned test patch is transferred onto the transfer means, the density thereof is measured, and one of multiple process parameters relating to the image formation means is adjusted based thereupon (Japanese Patent Laid-Open No. 63-43169). Furthermore, a method is known wherein exposure is made with various exposure amount in the range corresponding to the change in the light-portion potential estimated from the change in the environment, and the light-portion potential, which is to be a standard maximal density, is estimated based upon the pattern formed of the portions of different light-portion potential transferred onto the transfer means (Japanese Patent Laid-Open No. 1-261668). Furthermore, in addition to the above-described, a method is known wherein the change in the size of one dot is measured from the positional deviation of the pattern on the transfer means, and the process parameters such as an exposure period, output, a developing bias, and the like, are adjusted based upon the measurement results so as to maintain the suitable size of one dot (Japanese Patent Laid-Open No. 63-280275).
However, the above-described conventional image formation apparatuses have a problem in that in the event that the total count reaches a predetermined threshold number during processing, even for a job having just a few copies, the image formation apparatus enters an adjustment mode such as a density adjustment mode, leading to a problem of increase of time for processing the jobs beyond the anticipation of the user. There has also been a problem in that in the event that the image formation apparatus enters an adjustment mode, the tone or the like of the image formed may not be the same before and after the adjustment.